CRT Hercule Turbo no Modulation

[Wenefe]

Hello

I have a CRT Hercule Turbo

Unfortunately, it has no modulation in any operating mode

I would appreciate your help
Best regards from Austria

 

[Wenefe]

Hello

I have a CRT Hercule Turbo

Unfortunately, it has no modulation in any operating mode

I would appreciate your help
Best regards from Austria

 

[sp5it]

And that's a reason to post in old threads?
We unite in pain.
What measurements and tests you done so far?
Mike

 

[Wenefe]

And that's a reason to post in old threads?
We unite in pain.
What measurements and tests you done so far?
Mike

Thanks for the quick reply. The device was already with a technician, but unfortunately he gave up. Now I want to try it myself. I have measuring devices, soldering stations, etc. I just need a nudge in the right direction.

 

[sp5it]

Ok, lets start. Link schematic for your radio.
Mike

 

[19wrc333]

Ok, lets start. Link schematic for your radio.
Mike

The schematic can be found here: http://78roger.free.fr/crt/hercule_turbo.htm at the end of the service manual that is linked down there.

 

[sp5it]

Apply audio from signal generator on microphone socket, put it on TX and check if on pin1 marked blue you have a signal from generator. If not, follow red line back to mic socket to find where it disappear.
Mike

 

[Wenefe]

Thanks for your help.

I disassembled the device today.

I'll get a signal generator tomorrow.

Can someone show me where the IC is? I can't find IC 16 on the mainboard.

Best regards, Werner

 

[DTB Radio]

IC16 is an 8-pin DIP, 458.458 dual op-amp. It is used for amplifying the mic audio, and for handling transmit/receive switching. I've circled its location in yellow in the uploaded image.

Incidentally, this is the same chassis as the original RCI 2950/2970 radios and their base-station derivatives.

 

[BayouRadioAmplifier]

here is a tip on troubleshooting modulation problems
in these radios.

there is a built-in audio generator.

the "roger beep"

strong roger beep audio is fed in before that
mentioned double op-amp.

usually on these radios, the AMC and ALC is turned off,
and/or the components cut out. You hear it all the time,
the roger beep over modulates the signal. maybe causing
other problems, that I have seen.

Turn on the roger-beep. test that, for a over modulated
AM signal. if so, then the problem is up around the
MIC input circuit. you can check FM and SSB also.
A good fast test to get in the right direction of
low modulation problems.

I had a few of these RCI/Galaxy radio with weak AM TX.
Normal carrier power, low amplitude modulation.
the roger beep signal was piss-weak also.
The problem was that big electrolytic capacitor
in the modulator section C190, in series with the 15 ohm resistor.

I had another guys added external amp acting up.
told him to turn the roger-beep off. then all OK.

that is my $.05 worth (a nickel's worth) (inflation, and no more penny's)